Make Analyzer, VM and dart2js accept URI strings as part-of library identifier.

pkg/analyzer/test/generated/parser_test.dart

Index: pkg/analyzer/test/generated/parser_test.dart
diff --git a/pkg/analyzer/test/generated/parser_test.dart b/pkg/analyzer/test/generated/parser_test.dart
index 221755ab831d083c9e64d22756696652865137a3..b63ca01e71eea50679a850f2dd746b7cc3e33cfd 100644
--- a/pkg/analyzer/test/generated/parser_test.dart
+++ b/pkg/analyzer/test/generated/parser_test.dart
@@ -2318,7 +2318,7 @@ class Foo {
 
   void test_nonIdentifierLibraryName_partOf() {
     CompilationUnit unit = ParserTestCase.parseCompilationUnit(
-        "part of 'lib';", [ParserErrorCode.NON_IDENTIFIER_LIBRARY_NAME]);
+        "part of 'lib';", []);

[Brian Wilkerson, 2017/01/25 17:05:14]

We should still check that this error is emitted when the `of` is followed by an
invalid token. Perhaps change the test to "part of 3;".

[Lasse Reichstein Nielsen, 2017/01/26 10:39:13]

Done.

     expect(unit, isNotNull);
   }